For 64 entries, double elimination could work like this:
Song 1
Winner's Bracket Round 1
Song 2
Winner's Bracket Round 2
Loser's Bracket Round 1 & 2
Song 3
Winner's Bracket Round 3
Loser's Bracket Round 3 & 4
Song 4
Winner's Bracket Round 4
Loser's Bracket Round 5 & 6
Song 5
Winner's Bracket Round 5
Loser's Bracket Round 7 & 8
Song 6
Winner's Bracket Round 6 (Winner Finals)
Loser's Bracket Round 9 & 10 (Loser Finals)
Song 7
Grand Finals
Song 1
Grand Finals - Bracket Reset
Tiebreaker song can either always be song 7 or replay the same match.
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Pokemon VGC2011 NW Regional - Top 8
Pokemon VGC2011 US Nationals - 54th place